The Big Picture - Planetary Boundaries
- The earth is subject to the laws of physics.
- The earth is a finite source of resources.
- Living and non-living components of the earth interact and are interdependent.
Planetary boundaries are safe operating spaces in which we do not push the earth to irreversible damage. The stressors of human activities interact and add up. The consequences of not reducing the stressors is what pushes us outside the boundaries.
In 2009, former centre director Johan Rockström led a group of 28 internationally renowned scientists to identify the nine processes that regulate the stability and resilience of the Earth system. The scientists proposed quantitative planetary boundaries within which humanity can continue to develop and thrive for generations to come. Crossing these boundaries increases the risk of generating large-scale abrupt or irreversible environmental changes. 1
Scientists have defined these nine planetary boundaries:
- climate change
- biodiversity loss
- ocean acidification
- ozone depletion
- atmospheric aerosol pollution
- freshwater use
- biogeochemical flows of nitrogen and phosphorus
- land-system change
- the release of novel chemicals
Factors with one boundary segment may interact with factors in other boundary segment e.g.
- Invasive Species and Climate Change
- Australia's Massive Bushfires Spawned a Dramatic Heat Anomaly in The Stratosphere
- Australian Wildfires Linked to Ozone Layer Depletion
The Nine Planetary Boundaries diagram was updated in September, 2023. compare the 2019 version shown above with the new version shown below.
Six of nine planetary boundaries are currently transgressed. The length of the wedges symbolizes what the current state of the corresponding process is, in relation to the distance from the planetary boundary (end of the green area) and the Holocene baseline (origin of the diagram). The color symbolizes the risks associated with each. For example, a wedge may be very long because the current state is already very far from the planetary boundary and the Holocene. But it may still not be purple, because that is not yet associated with very high risks in this particular case. In other cases already a "small" overshoot (short wedge) results in a big risk: Then the color further inside already changes to purple. Illustration: Richardson et al., Science Advances, 2023 (CC BY-NC 4.0)